In a number of industries it is desirable to use storage containers that seal. For example, glass bottles sealed with cover closures, called "bottle caps," are used by beverage manufactures to store beverages. Bottle caps generally include a circular top panel, a cylindrical skirt extending from the peripheral edge of the top panel, and a liner. The liner is disposed on the inside of the top panel. The liner usually includes a raised sealing ring, which mates with the bottle to form a seal.
A number of different processing steps go into properly forming bottle caps. The liner, which is commonly formed of plastics such as polyvinyl chloride resin is molded into the cap at an elevated temperature. Formation in this way imbeds gases or volatiles within the liners. As the liners age, these gases can escape and reduce the purity and potentially the flavor quality of the bottle's contents. Therefore, it is desirable to have a process for removing these gases during manufacture.
In an effort to prevent bottle caps from sticking to various machine parts during processing, it is desirable to cool the liners after molding. U.S. Pat. No. 4,260,483 issued to Nicholson et al. discloses one method of cooling bottle caps using a cooling station with a conveyor belt. The belt moves slowly so that ambient air contacts and cools the liners. In this patent there is a concern about cooling the liners too quickly, so an enclosure is placed over the conveyor to further slow cooling. In order for this cooling station to work at a rate that is compatible with automated molding machine, rows of caps are processed on the conveyor at the same time. However, this type of set up may require a significant amount of space for the conveyor belt.
Another aspect of manufacturing bottle caps is related to a number of liner defects that occur. One defect occurs when the cap is formed without the liner. When a liner-free cap is applied to the bottle, this empty cap is not sealed. Another defect occurs when the liner sealing ring is formed with internal gaps or voids or formed in the improper shape. Any of these defects in the ring can result in a poor seal, which results in the undesirable consequences of air or contaminants entering the container. Another consequence is that a poor seal may lead to the contents of the bottle spoiling. For some applications, it is also considered a defect when a portion of the liner is molded on the cap skirt. This misplaced liner may prevent the cap from properly fitting on the container. If the cap is loose enough, the contents of the bottle may spill or the bottle may have a poor seal. A more serious consequence of the misplaced liner occurs when such a liner strains an automatic capping machine to the point where the glass container ruptures. If this occurs during manufacturing, the machines are stopped and possibly serviced, which is costly.
In an effort to minimize the consequences of defective caps, processing bottle caps typically includes inspecting the lined caps. Properly lined caps are shipped for use, and improperly lined caps are rejected and not used. Inspection can be manual or automated. In an automated, high-production environment it is desirable to inspect the caps at the cap processing rate, which is the speed at which the liners are molded. Since manual inspection is too slow to keep up with the cap processing rate, automated inspection machines are preferred.
Several patents have been issued which are directed towards automated inspection machines. For example, U.S. Pat. No. 3,724,655 issued to Clark discloses an apparatus for testing gasket thickness and sealing, and rejecting caps with gaskets that are not without a predetermined thickness range or that do not seal properly. The testing apparatus includes a memory wheel with movable pins. The position of the pins is used to sort unacceptable from acceptable caps. As the use of the memory wheel makes the testing apparatus complex and increases testing time; this solution is less desirable and thus not a preferred one.
The present invention is intended to provide a method and apparatus for processing lined caps in a simple yet efficient manner by cooling the lined caps, removing volatiles from the lined caps, and inspecting the lined caps while operating at the cap processing rate.